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Recent explanations for the evolution of eusociality, focusing more on costs and benefits than relatedness, are largely untested. We validate one such model by showing that helpers in foundress groups of the paper wasp Polistes dominulus benefit from an insurance-based mechanism known as Assured Fitness Returns (AFRs). Experimental helper removals left(More)
The reactions of cis-[PtCl(NH3)2(H2O)]+ with L-methionine have been studied by 1D 195Pt and 15N NMR, and by 2D[1H, 15N] NMR. When the platinum complex is in excess, the initial product, cis-[PtCl(NH3)2(Hmet-S)]+ undergoes slow ring closure to [Pt(NH3)2(Hmet-N,S)]2+. Slow ammine loss then occurs to give the isomer of [PtCl(NH3)(Hmet-N,S)]+ with chloride(More)
Many signals encountered in passive sonar are approximately cyclo-stationary in that a given waveform is repeated at almost a constant rate. The underlying physical process causing the sound is often a complex train of nonidentical impulses. The ability to track the frequency of these pulses over time can be used in such things as detection, classification(More)
The cepstrum transform can be used to determine the periodicity of an input si@. There are cases where the cepstrum fails. The input signal may contain very few b o n i c s , or contain only odd harmonics. There may be a c h q in the input signal which will broaden the spectral components. It is possible to improve the cepstrum's operation by mtroducing(More)
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